#include<bits/stdc++.h>
//#pragma GCC optimize(3,"Ofast","inline")
//#define int long long
#define i128 __int128
#define ll long long
#define ull unsigned long long
#define uint unsigned int
#define ld double
#define PII pair<int,int>
#define INF 0x3f3f3f3f
#define INFLL 0x3f3f3f3f3f3f3f3f
#define chkmax(a,b) a=max(a,b)
#define chkmin(a,b) a=min(a,b)
#define rep(k,l,r) for(int k=l;k<=r;++k)
#define per(k,r,l) for(int k=r;k>=l;--k)
#define cl(f,x) memset(f,x,sizeof(f))
#define pcnt(x) __builtin_popcount(x)
#define lg(x) (31-__builtin_clz(x))
using namespace std;
void file_IO() {
//	system("fc .out .ans");
	freopen(".in","r",stdin);
	freopen(".out","w",stdout);
}
bool M1;
const int N=1e5+5,M=5e5+5;
int head[N],len;
struct node {
	int to,w,nxt;
}; node edge[M<<1];
void add_edge(int u,int v,int w) {
	edge[++len]={v,w,head[u]}; head[u]=len;
}
int dfn[N],low[N],p;
vector<int> vec;
void tarjan(int u,int bl) {
	low[u]=dfn[u]=++p;
	for(int i=head[u];i;i=edge[i].nxt) {
		int v=edge[i].to,w=edge[i].w;
		if(!dfn[v]) {
			tarjan(v,w);
			if(low[v]>dfn[u])
				vec.push_back(w);
			chkmin(low[u],low[v]);
		} else if(w!=bl)
			chkmin(low[u],dfn[v]);
	}
}
int a[N],b[N];
void solve() {
	int n,m;
	scanf("%d%d",&n,&m);
	rep(i,1,m) {
		scanf("%d%d",&a[i],&b[i]);
		add_edge(a[i],b[i],i);
		add_edge(b[i],a[i],i);
	}
	rep(i,1,n) {
		if(!dfn[i])
			tarjan(i,0);
	}
	sort(vec.begin(),vec.end());
	for(auto x:vec)
		printf("%d %d\n",a[x],b[x]);
}
bool M2;
signed main() {
	//file_IO();
	int testcase=1;
	//scanf("%d",&testcase);
	while(testcase--)
		solve();
	fprintf(stderr,"used time = %ldms\n",1000*clock()/CLOCKS_PER_SEC);
	fprintf(stderr,"used memory = %lldMB\n",(&M2-&M1)/1024/1024);
	return 0;
}